1. Field of the Invention
The present invention relates to a hydraulic brake, and more particularly to a hydraulic brake assembly used to apply opposing brake loads on the wheel rim of a vehicle such as a bicycle, a motorcycle, and the like.
2. Description of Related Art
A conventional rim brake in accordance with the prior art comprises a pair of left and right arms pivotally attached to a frame of a bicycle, each having on its distal end portion a brake shoe, and a spring for energizing the arms to move toward brake releasing direction. When braking, each arm pivotally moves toward a rim such that each brake shoe forces against the rim to brake. The movement of each arm is angular such that an upper/lower edge of each brake shoe abuts against the rim first. This pivotal type of load application results in inefficient braking force due to play in the pivots and the none-parallel contact between the brake shoe and rim results in uneven wear Furthermore, in the case of a road bike, the left and right arms rotate about a central pivot this arrangement makes them very prone to twist under the resulting braking torque making the braking performance inefficient, especially in the case of ultra-light brakes which have become the market trend. Moreover, the arms need to rotate to achieve the braking load and because the conventional rim brake needs to be mounted to the head tube of the bicycle frame and a heavy duty return spring must be accommodated for releasing the arms, these become the limiting factors when trying to design ultra-light rim brake. In addition, the conventional rim brake employed on mountain bikes are composed of the left and right arms, the two-piece structure of the conventional rim brake relies on brake load being transferred from one side rim to the other by reaction forces, if not carefully set-up this may not provide a stable supporting force such that the brake force is unbalance.
A conventional hydraulic brake in accordance with the prior art comprises a hydraulic cylinder, a piston movably received in the axial direction of the cylinder, and a brake pad connected to the piston. When braking, the piston moves toward a disk such that the brake pad forces against the disk to brake. The conventional hydraulic brake improves the structure for providing a stable brake force to the disc. However, the conventional hydraulic brake is cooperated with the disc and the brake load is applied to one side of the wheel which can result in twisting effect of the front wheel. The use of a disk limits the manufacture and assembling of the conventional hydraulic brake to the bike. In addition, the cost of the conventional hydraulic disk brake is high such that the tolerance of the cylinder bore and the piston diameter are critical. The weight of the conventional hydraulic disk brake is heavy. Moreover, most road bicycle frames are designed for the traditional caliper road brakes and no mountings are present for more powerful hydraulic brakes. Additionally some MTB bicycles are designed to fit only conventional V-brakes or standard disk brakes.
The present invention has arisen to mitigate and/or obviate the disadvantages of the conventional rim brake and disk brake.